Organic photovoltaic devices (OPV) based on π-conjugated polymer and fullerene composites, so-called “bulk heterojunction (BHJ)”, offer an intrinsically low-cost, scalable approach to photovoltaic technology.1,2 Important examples of materials used for fabricating BHJ solar cells include blends of thiophene-based polymers as electron-donors (D) and fullerene derivatives as a electron-acceptors (A).3-10 Synthetic effort has focused on improving the power conversion efficiencies (PCE) by means of development of low band-gap polymers8,9 and fullerene derivatives.7,10 With the goal of obtaining improved performance, control of the morphology within the BHJ material has utilized processing additives,11,12 different solvents (and mixed solvents),13 and thermal annealing.14-17 These different methods attempt to facilitate the phase separation on length scales of a few nanometers in the devices4,16 
Rod-coil di-(AB-type) copolymers constitute a class of macromolecules that can be uniquely fashioned into self-assembled nanostructures in which the rod blocks align along their long axes into nanoscaled domains, often creating liquid crystalline mesophases.18-23 Therefore, in case of the rod-coil block copolymers containing a rigid conjugated polymer segment as a rod block, their ability to self-organize can be used optimize the morphology in OPV devices.
Reports on rod-coil block copolymers based on P3HT rod and polyolefin coil by using living radical polymerization techniques have established the existence of nanofibrilar structures in the solid state.24-28 Although there are reports of synthesis directed toward soluble donor-acceptor rod-coil diblock copolymers containing C60 for use as the active layer in solar cells,29-32 the difficulty in removing unreacted C60 has limited the success of this approach. Moreover, these soluble donor-acceptor rod-coil diblock copolymers containing C60 have not been reported with an exclusive nanofibrilar structure.
Recently, Fréchet et al. have demonstrated the synthesis of a well-defined donor-acceptor amphiphilic diblock copolymer by using ring-opening metathesis polymerization (ROMP). They showed that the diblock copolymer can play a critical role in tuning the device morphology when employed as an additive, leading to stabilization of the device structure against destructive thermal phase segregation.26 Thus, the synthesis and characterization of well-defined “donor-acceptor rod-coil” diblock copolymers promises to be of use in obtaining self-assembled nanostructures in materials for OPV.